The invention relates to a fuel injection system for an internal combustion engine, comprising at least one fuel injection nozzle.
A device is known, from JPH03182680 A, in which a fuel injection nozzle of an internal combustion engine is arranged in a bore of a cylinder head. The device has a holding device which is designed in the manner of a two-arm lever and which engages at one side with a first arm on a collar-like stop of the fuel injection nozzle and at the other side with a second arm on a bolt head of a cylinder head bolt. A fastening bolt extends between the two arms, which fastening bolt is screwed into a thread in the cylinder head and braces the fuel injection nozzle against a stop in the bore of the cylinder head with the interposition of a seal. Furthermore, a nozzle tip of the fuel injection valve extends through a passage opening in the cylinder head and is thereby connected to a combustion chamber of the internal combustion engine.
DE 195 54 065 A1 discloses an assembly for fastening an injection nozzle in a holder which is equipped with a receiving opening for the injection nozzle. A bracing element is attached to the injection nozzle. By means of fastening bolts, the bracing element is connected to the holder, specifically such that the injection nozzle bears with a force fit against a stop in the receiving opening. A sealing disk is installed between the injection nozzle and stop. Also, a nozzle tip of the injection nozzle extends through a passage bore in the holder, such that fuel can be introduced into a downstream combustion chamber.
It is an object of the invention, for a fuel injection nozzle of a fuel injection system which operates in an internal combustion engine, to devise measures which firstly hold the fuel injection nozzle securely in position on the internal combustion engine and which secondly promote simple installation of said fuel injection nozzle. Here, it should however also be sought to achieve that the measures can be implemented with means which substantially involve little outlay.
According to the invention, said object is achieved by a fuel injection system for an internal combustion engine, comprising at least one fuel injection nozzle which, by way of a cylindrical shell body, is inserted at least in regions into a bore of a cylinder head and which, by way of a nozzle tip, feeds fuel to a combustion chamber between the cylinder head and a reciprocating piston. The fuel injection nozzle is held in position on a housing section of the internal combustion engine with the interposition of a holding device, which holding device braces a first end region of the fuel injection nozzle against a bore stop within the bore in the cylinder head. The holding device has, outside the bore, a fixing bushing to which the shell body is fixed axially and radially by way of a radial insert element. A spring system acts between a first radial stop of the fuel injection nozzle and a second radial stop of the fixing bushing as viewed in the axial direction of the shell body of the fuel injection nozzle. The spring system seeks to move the fixing bushing, by way of a third radial stop, against a locking element system of the insert element, which is supported on a fourth radial stop applied to the shell body.
The main advantages achieved by the invention can be seen in that it is exemplary from a design aspect that the holding device of the fuel injection nozzle has, outside the bore in the cylinder head, the fixing bushing to which the shell body of the injection valve is fixed axially and radially by the radial insert element. Here, the spring system acts between the first radial stop of the fuel injection nozzle and the radial stop of the fixing bushing as viewed in the axial direction of the shell body. The spring system seeks to move the fixing bushing, by way of a third radial stop, against the locking element system of the insert element, which is supported on the fourth radial stop applied to the shell body.
It is exemplary that the insert element is in the form of a U-shaped fixing clip which is made up of two parallel limbs and a transverse web which connects said limbs, the limbs of the first and second locking elements and the transverse web forming the third locking element. In this regard, it is to be emphasized that at least the first and second locking elements have a square cross section. It is expedient from a structural aspect that the first and second locking elements have inner delimitations and outer delimitations as viewed in the radial direction of the metal body of the fuel injection nozzle. The inner delimitations interact with first flattened portions of the metal body and the outer delimitations interact with second flattened portions of the fixing bushing. For optimization of the fixing clip, it is also conducive that its transverse web is, as viewed in the radial direction of the shell body, fixed by an axial securing collar of the fixing bushing.
With regard to the spring system, standards are set by the fact that it is formed in a ring-shaped manner between the first stop of the shell body and the second stop of the fixing bushing. This is achieved in that the spring system is formed by a spring device composed of rubber or elastomer and a compression spring composed of spring steel, which spring device and compression spring are situated one behind the other as viewed in the axial direction, the compression spring being supported against the first stop and the spring device being supported against the second stop. It is also of note that the spring device is of double-T-shaped form in cross section and, by way of the limbs connected to the transverse web, acts as a sealing body between the first flattened portions of the shell body and the second flattened portions.
A design which is sophisticated from a strength aspect can be realized in that the fixing bushing is, in the direction of the second end region of the fuel injection nozzle, equipped with a jacket cup which has a first, conical shell section leading away from the fixing bushing, with a second, cylindrical shell section adjoining said first shell section. Furthermore, the second shell section is neatly delimited by the support flange.
An excellent design is realized in that the fixing bushing, the first shell section and the second shell section are combined as a high-strength bearing bracket produced in one piece. A further possible use of the bearing bracket is made possible by virtue of the bearing bracket being designed for receiving two fuel injection nozzles, wherein a single fastening bolt which extends, in a central longitudinal plane between the injection nozzles, through a bracket bore, which is surrounded by a turned-up reinforcement of the bearing bracket, serves for fastening the bearing bracket to the housing section of the internal combustion engine. It is also expedient that a sealing device is provided between the support flange and a contact plane of the housing section. It is groundbreaking from a manufacturing aspect that the bearing bracket, the fuel injection valves, the spring systems and the insert elements form a prefabricated structural unit.
Finally, for the installation of the fixing clips, which are in the form of insert elements, an ingenious method is suitable in which the spring systems and, subsequently, the fuel injection nozzles are inserted into the fixing bushings of the bearing bracket. The respective fixing clips then are subjected, via the first stop, to load in the axial direction of the fuel injection nozzle such that the insert element can be inserted radially, in such a way that the securing collar of the fixing bushing engages over the transverse web of the fixing clip such that the fixing clip is radially secured after the spring system is relieved of load.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.